Chemical process and products



fluoride or with metallic fluorides.

Patented July 2, 1946 CHEMICAL PROCESS AND PRODUCTS Paul L. Barrick,WilmingtomDeL, assig-nor to E. I. du Pont de Nemours & Company,Wilmington, Del a corporation of Delaware No Drawing. Application March8,1943, Serial No. 478,417

This invention relates to the preparation of fluorinated organiccompounds and to new organic fluorine compounds. More particularly, theinvention comprises a new process for the preparation of polyfluo'roorganic acids and includes new chemical products consisting ofpolyfluoro organic compounds containing a sul'fonyl group.

It has previously been proposed to produce or ganic fluorine compoundsby the reaction of fluorine with various organic materials. Priorinvestigations have shown that this reaction of fluorine results invigorous or explosive reactions, accompanied by charrin'g. Accordingly,the directfaction of fluorine on organic materials has not been'usefulas a means for preparing organic fluorides.

Heretofore, the usual method for preparing organic fluorine compoundsconsisted in reacting halogenated organic compounds with hydrogenHowever, such processes yield a mixture of products, involveconsiderable expense-and their application is restricted to certaintypes of halogenated compounds.

It is an object of this invention 'to provide a new process for thepreparation of vpolyfiuoro organic acids without using dangerous orexpensive inorganic reagents. Ancithercbject of this invention is toobtain new compositions of matter consisting of organic fluorinecompounds containing a sulfonyl group. Still another object is toprovide a new process for readily preparing difluoroacetic acid, itssalts and derivatives. A further object is to provide a process 'forpreparing polyfluoroethanesul'fonic acids, their salts and derivatives.A still further object is to obtain new compounds consisting ofpolyfluoroethanesulfonic acids, their salts and derivatives-whichpossess many noveland useful properties. Other objects will appearhereinafter.

These objects are accomplished by reacting a polyfluoroethylenecontaining at least two fluorine atoms, two of which .are attached toone carbon atom, with a'sulfurous acid salt. This reaction producespolyfiuoroethanesulfonic acid salts which may be converted to thecorresponding acids and their derivatives. 7 By employing apolyfluoroethylene such as tetrafluoroethylene, there is also obtaineddifluoroacetic acid salts which maybe converted to the correspondingacid and its derivatives.

A preferred form of the invention may be carried out by reactingtetrafluoroethylene with an aqueous solution of a sulfurous acid salt. Amixture is obtained containing tetrafl'uoroethanesulfonic acid salts anddifluoroacetic acid salts. These 'fluorinated organic salts are readilyseparated from "the inorganic salts by evaporating the reaction mixtureto dryness and extracting with 17 Claims. (Cl. 260-513) pho'ruspentachloride.

:Sulfurou's acid salts, as used herein, designate an inorganicwater-soluble sulfurous acid :salt containing a metal orinorganiciradical which will yield a water-solubleisalt. The'alkalimetal-sulfurous acid salts are preferred for use in this invention;However, the invention is applicable generally to inorganicwater-soluble sulfurous acid sa-l-ts'and to water-soluble alkali andalkaline earthsulfites and ibisulfites.

The polyfluoroethylenes suitable for usein this invention may berepresented by the general for- .mula CXz=CX2, where two Xsattached toone-of the 'carbonatoms are fluorine and the other :two Xs are selected.from the group consisting of :hy-'- drogen and halogen. It isxpreferableto usepolyfluoroethylenes containing #at least three :halogenatoms, of which at least two are fluorine. Thus in the general :formulaone .X would .be selected from the group consisting of hydrogen andhalogen and the other three Xs would be halogen, 'of

which at least two attached to one carbon atom would be fluorine.Tetrahaloethylenes containing at least three :fluorine'xa-tomsare themost preferred group of polyfluoroethylenes.

The p'olyfluoroethanesulfonyl compounds obtained by the presentinvention may be represented by thegeneral formula imcxcxp 'sozoim lenceof M. Thus the'polyfluoroethanesulfonic acids of this invention may berepresented by the general formula 'H 'CX2CX2)-SO2O'H where two Xsattached to one carbon atom are fluorine and the othertwo Xs areselected from the group consisting of hydrogen and halogen. It isunderstood that the unit in parenthesis represents the particularpolyfluoroethylene employed. With "the'un'symmetrica'lpolyfluoroethylenes, it is possible that two isomeric products may beobtained.

However, with tetrafluoroethylene only one salt would be obtainedrepresented -by the formula'e incrtcrwsozlnm theaiii being'representedbythe formula HCFzCFzSOzOH The polyfluoroethanesul-fonates,. such asthesedium 'salts,-'-or the sulfonic acids may be converted into thecor-responding sulfonyl chlorides by reaction with phosphorus chlorides,such as phos- Thus, the salts or the acid obtained from sulfurous:acidsalts and tetrafluoroethylene there is producedtetrafluoro-"ethanesulfonyl chloride 'reaction.

[HCFzCFzSOzCl]. .The sulfonyl chlorides can be readily 'convertedint'osulfonamides by reaction with ammonia; or primary or secondary amines.

The most general formula representing the new" polyfluorosulfonylproducts of this invention is 'H(CX2CX2)Z where two Xs attached to oneof the carobn atoms are fluorine, the other two Xs' are selected fromthe groupconsis'ting of hydro- 1 gen and halogen, and Z is a monovalentradical containing a sulfonyl group of which the sulfur atom is directlyconnected to carbon of .the

The method for carrying out the reaction varies to some extent withdifferent polyfluoroethylenes and sulfurous acid salts, but the usualprocedure comprises charging waterand the sulfurou acid salt into a highpressure reaction vessel, adding a given amount ofpolyfluoroethylene,-such as tetrafiuoroethylene, and then closing thereaction vessel'and heating to the desired'temperature whilemechanically agitating the reaction vessel for several hours. Thefluorinated organic salts are separated from the inorganic salts byevaporating the reactionmixture to dryness, extracting with alcohol, andthen evaporating off the alcohol. Although the sulfonic acid salt can bepartially separated from the difluoroacetic acid salt 'by fractionalcrystallization, it is preferable to convert the salts into thecorresponding acids and to separate the acids by fractionaldistillation.

" I The temperature at which the reaction is effected may be varied overa wide range depending largely upon the nature of the reactants, the

Catalysts such as oxygen andperoxygen com pounds may be used in theprocess of this invention although such catalysts are not necessary. .Itis often advantagecusto add various inorganic salts such as borax ordisodium phosphate which exert a buffering action and help keep thereaction, mixtureffromQbecoming strongly acidic which has a tendency tostop the reaction. In

general, it is desirable to have the pH of the- .aqueous solution above3.5 at room temperature and the preferred pH ran e for preparing thepolyfluoroethanesulfonate salts is 4.5 to 10.5. .The yield of thedifluoroacetic acid salts increases with increase in pH and ifone wishesto prepare difluoroacetic acid salt in appreciable amounts a pI-l above8 is desirable. It is understoodthat other halogen-substituted aceticacid salts may be obtained by using polyfluoroethylenes other thantetrafluoroethylene, Thus, whentrifluorm' chloroethylene is used,difluoroacetic acid salt, fiuorochloroacetic acid saltor a mixture ofthe two salts maybe obtained. Similarly, difluoroacetic acidv salt,monofluoroacetic acid salt or mixtures thereof may be obtained whentrifluoroethylene is used.

1: The proportion of waterin the reaction mixi- ,ture. may varywithinrelatively wide limits der ndinglars y up n thenature f t e re t sfiltered to remove a small amount of coarse nonand products. Eflicientreaction may be effected I using dilute or saturated aqueous solutionsof the sulfurous acid salts. Since the sulfonic acid salts formed areusually much more soluble than the original inorganic sulfurous acidsalts, an excess of the solid sulfurous acid salt over a saturatedsolution may be placed in the bottom of the reactor and' as the reactionproceeds more and more will dissolve in the water. Thus; it is possibleto carry out reactions with sulfurous acid "salts which are onlyslightly soluble in water in convenient sized equipment.

The invention is further illustrated by the following examples in whichthe parts are by weight 7 unless otherwise specified.

a ple I A mixture of parts of sodium sulfite and 200 parts of water wascharged into a.si1Ver-,

lined autoclave and after evacuating the system, the autoclave waspressured with tetrafluoroethylene to 350 lbs/sq. in. at C. andrepressured to 350 lbs/sq. in. with tetrafiuoroethylene when thepressure dropped to about 325 lbs/sq. in. during the run. The reactionproceeded smoothly and over a period of 9 hours at 120 C. there was atotal pressure drop of about 1270 lbs/sq. in. The reaction mixture had apH of 10.2 and was fusible. solid (11.4 parts) which corresponded tosodium fluoride in composition. The filtrate was evaporated to drynessand the solid residue treat- .ed with hot absolute ethanol and filteredto remove the alcohol-insoluble inorganic salts such as sodium sulfiteand sodium fluoride. The col-' orless salt obtained by evaporating offthe alcohol amounted to 177 parts and was found to consist of a mixtureof sodium tetrafiuoroethanesulfonate and sodium difluoroacetate meltingat about 160C. Although the salts can be separated by fractionalcrystallization from various solvents,

it'was' found more convenient to convert the salts into thecorresponding acids and to separate the.

acids by fractional distillation. About 439 parts of the alcohol-solublesodium tetrafiuoroethanesulfonate and difiuoroacetate salts obtained asdescribed in this example without removing the last traces ofa'lcoholwere treated with about 500 parts of 35% sulfuric acid and filtered toremove the solid precipitate. of sodium sulfate. The filtrate wasextracted several times with ether and the ether extracts combined andrectified. Considerable water and low boiling material were obtainedwhich consisted of about 10 parts ethyl difiuoroacetate boiling at96-100 C. and 15 parts of difluoroacetic acid boiling at 132133.5 C.However, the main'product boiling at 110 C./3 mm. wastetrafluoroethanesulfonicacid monohydrate and amounted to about 248parts. sulfonic acid-monohydrate was solid at room temperature, meltedat about 54 C. and was extremely hydroscopic.

Neutral F S I equivalent Percent Persian/t Analysis; 37. 90 16. 10 198.8 Calc. for HCFZQFZSOZH.H20 38. 00 16.0 V 200 'A mixture of 96 parts oftetra'fluoroethanesul- 7 fonic acid-monohydrate described above and.parts of thionyl chloride were warmed gently for about an hour and themixture rectified. After removing the unreacted thionyl chloride, 31parts The.

F l 01 S Analysis of traction boiling 'iit 1 mm: Percent Percent 90-92 C36.25 17 14.87 Calc. for HCFgCFnSOgCl 37.9 17. 73 I 15. 95

Example II A mixture of parts of sodium bisulfite, 200 parts of water,50 parts of bor'ax and 1 part of benzoyl peroxide, having a pH of about'7 was charged into a silver-lined autoclave and after pressuringwithtetrafluoroethylene to 150 lbs. /sq. in. the reaction mixture washeated at 120 C. with agitation for eight hours. The'syst'em wasrepressured with tetrafluoroethylene to 150 lbs/sq. in. when thepressure dropped to about 125 lbs/sq. in. during the run. The reactionproceeded smoothly and a total pressure drop of about 355 lbs/sq. in.was obtained. On working up the reaction mixture as described in ExampleI, 28 parts of alcohol-soluble salts were obtained meltingat about 295C. which consisted principally of sodium tetrafluoroethanesulionat (F,35.75%; S, 14.98%; Na, 11;81%).

Example III A mixture of 100 parts of potassium sulfite, 150 parts ofwatenand 1.5 parts of benzoyl peroxide were charged into an autoclaveand the system. evacuated'and pressured with tetrafluoroethylene I to350 lbs/sq, in. at 120 C. as described in Exam ple I. A total pressuredrop of about 1180 lbs/sq. in. was observed and 186 parts ofalcohol-soluble products consisting of potassiumtetrafluoroethanesulfonate "and potassium difluoroacetate.

were obtained. v

The reaction products were Worked up as described under Example I andyielded similar cohol yielded a colorless solid which melted at about294 C. when heated on a copper block in the air. After drying for sometime at about 105 C., the sodium tetrafiuoroethanesulfonate wasanalyzed.

F -s Na Percent Percent Percent FOlllld 37. 4 15. 71 11. 34 Calc. for CHF4S OaNa r 37. 3 15. 7 11.27

Eight parts of tetrafluoroethanesulfonic acid wa'sadded slowly to anexcess of aniline. A vigorous reaction occurred and a solid separated.The excess of aniline was filtered (iii and the solid product washedthsrcugmywimetner. The

. Neutral F N S equiv.

Per- Pzr- Perc nt amt cent Found 28.58 5. 23 11.156 274. 3; 273.3Gala-for HC F-4SOaH.NH CaH5 27. 65 5.09 11.65 275 The above salt is alsoobtained when tetrafluoroethanesulfonic acid-monohydrate is reacted withv phenylisocyanate.

Example 7V An autoclave was flushed with nitrogen and "charged withmparts of sodium sulfit'e, 1-50'part's of distilled water and 25 partsof vinylidenefiuoride. The reaction mixture was heated ab- C. for "8hours and then evaporated to dryness and extracted with absolutealcohol. There was obtained 6.7 parts-of alcohol-soluble salts whichmelted at about 274-278 C. andwhich-contained 17.43% fluorine, 12.79%sulfur, and 14.76% *sodium.

Among the polyfiuoroethylenes whichare applicable in this invention aretrifluorochloroethylene, trifluorobromoethylene, trifluo'roiodoet'hylene, trifiuoroethylene, 1,1-difluoro-2,2-dichloroethylene,1,l-difluoro-Z-ch1oroethy1ene, and vinylidene fluoride.'Te'trafiuoroethylene 'is 'a'rticu larly preferred for use in thisinvention.

Examples of water soluble alkali and alkaline earth sulfites andbisulfites suitable for use inthis invention are those of sodium,potassium, ammonium, lithium, magnesium and calcium.

iIt will be understood that the operating conditions may vary widelydepending upon the nature of the compounds being reacted and also uponthe results desired. The time required for carrying out the reactionsmay vary from a few minutes to several days depending upon the hature ofthe reactants and the other operating conditions such as temperature'andpressure.

The process may be operated continuously or intermittently. The reactionmay be carried out in a closed system or the reaction may b carried outby bubbling the vapors of the polyfluoroethylene through a columncontaining the aqueous solution of the sulfurous acid salt. In general,the reaction is carried out under subatr'no'spheric, atmospheric orsuperatmospheric pressure in the range .1 to 1000 atmospheres. Thepreferred pressure range is 1 to 200 atmospheres.

Although generally it is preferable to use aqueous solutions, in certaininstances it maybe desirable to add small amounts of organic solvents.The polyfluoroethylene employed may contain stabilizers such astributylamine or Te'rpe'ne B hydrocarbon which exert no deleterious-eff'ect'on the present reaction.

The reactions may be'ca'rried out many suitable reaction vessel such asstainless steelfiron, enamel, silver, aluminum, and other metals andalloys which are capable of withstanding heat and pressure. The reactionis preferably carried out with agitation, although agitation'is'notalways necessary. I The reaction and the separation or isolation of theproducts may be carried out simultaneously or in separate steps. Theproducts inay be separated methylamine, v aniline,

amaze? by evaporation and extraction with alcohol or by acidifyingwith astrong mineral acid and distilling or extracting, or by any otherconvenient method. A convenient method for separating sodiumdifluoroa'cetate from sodium 'tetrafluor'oethanesulfonate consists inacidifying w'ithhydrochloric acid and distilling to'remove the di-'fluoroacetic acid and excess hydrochloric acid. Thetetrafiuoroethanesulfonate salt can then be separated from the sodiumchloride by extract! ing with absolute ethyl alcohol.

v'I'he present invention is useful for the production of a wide varietyof organic fluorine-con taining sulfonic acids and derivatives. Thepolyfluoroethanesulfonate salts can be converted into the correspondingsulfonic acids by acidifying with'a strong mineral acid such assulfuric, or phosphoric acid and can be separated by distilling orextracting with ether. The polyfluoroethanesulfonic acids are strongacids, very soluble in water, stable to distillation and readily formwater-soluble saltswith organic and inorganic bases such as ammonia,primary, secondary, andtertiary amines, methyl amine, dimethylamine,tri- -naphthaylamine, N- monomethyl aniline, morpholine, dodecylamine,

" hexarnethylenediamine, amino acids, hydrazines,

and with hydroxides and basic salts of sodium, potassium, lithium,calcium, barium, aluminum,

.zinc, iron, copper, lead, and bismuth. Thus, tetrafiuoroe'thanesulfonicacid readily forms water'- soluble salts" with inorganic bases'to yieldsalts such as sodium, potassium, calcium, barium, lead, iron, bismuth,zinc, magnesium, and nickel salts.

Also tetrafiuoroethanesulfonic acid readilyfforms water-soluble ammoniumor substituted ammonium salts with ammonia, primary, secondary andtertiary organic amines.

The products of this invention are useful for various commercialpurposes' The sulfonic acids of this invention are strong stable acidswhich are soluble in various organic solvents and can be usedadvantageously in place of sulfuric acid, for example, as catalysts invarious reactions in which sulfuric acid causes excessive charring. Manyof the products'have been'found to be very desirable in that they aresubstantially nonflammable.

The polyfluoroethanesulfonic acids and salts prepared in accordance withthis invention have outstanding thermal and chemical stability.

The'invention is particularly advantageous in that it offers a safe,flexible, practical and coo-- nomical method of producing highlyfiuorinated products of the character herein described. One of theadvantages of the invention is that the process may be operated withoutcatalyst and the reaction proceeds smoothly and easily.

As many apparently widely different embodiments of this invention may bemade without departing from the spirit and scope thereof, it is to beunderstood that I do not limit myself to the specific embodimentsthereof except as defined in water-soluble inorganic sulfurous acidsalt.'

4. A process for the production of salts of polyfluoro organic acidswhich comprises reacting a polyfiuoroethylene containing at least threehalogen atoms of which at least two are fluorine and. are attached toone carbon atom with an aqueous solution of a water-soluble inorganicsulfurous acid salt. v a

5. A process for the production of salts of polyfluoro organic acidswhich comprises reacting a polyfluoroethylene containing at least threefluorine atoms with an aqueous solution of a watersoluble inorganicsulfurous acid salt.

6. A process for the production of salts of polyfluoro organic acidswhich comprises reacting at an elevated temperature under pressure apolyfluoroethylene containing at least three fluorine atoms with anaqueous solution of a water-soluble ethanesulfonates anddifluoroacetates which comprises reacting tetr'afluoroethylenewith anaqueous solution of a member selected from the class consisting ofsodium and potassium sulfites and 10. Th mical compound1,1,2,2-tetrafiuoroe 'anesulfonic' acid; 7

11. A polyfluoro organiccompound of the general formula I-I(C{X2CX2)Z awhere two Xs attached to one carbon atom are fluorine, the other two Xsare selected fromthe group. consisting of hydrogen and halogen, and Z isa monovalent radical containing a sulfonyl group of which the sulfuratom is directly connected to carbon of the (CXzCXz) group.

12. A polyfiuoroethanesulfonyl compound of the general formula where twoXs attachedto one carbon atom are fluorine, the other two Xs areselected from the group consisting of hydrogen and halogen, M is amember selected from the groups consisting of hydrogen, metals andinorganic radicals which will yield a water-soluble inorganic sulfurousacid salt, and n is a positive integer equal to the valence of M. I

13. A tetrafluoroethanesulfonyl compound the general formula where M isa member selected from the group consisting of hydrogen, metals andinorganic radicals which will yield a water-soluble inorganic sulfurousacid salt, and i1. is a positive integer equal to the valence of M. Y

14. A tetrafluoroethanesulfonyl compound of the general formula where Zis a monovalent radical ccntaininga sulfonyl group of which the sulfuratom is directly connected to carbon of the (CFaCFz) group.

15. A process for the production of difluoroacetic acid salts whichcomprises reacting tetra-

